Known machines for the driving of underground cavities, such as tunnels, adits, underground roadways and the like of the partial-cut type have a vertically and laterally pivotable cutter arm carrying a driven cutter head on its free end. In order to cut a predetermined tunnel cross-sectional profile with sufficient accuracy and ensure the tunnel progresses with high directional accuracy, in the past numerous methods and control apparatuses have been developed. It is known to use a light beam created by a laser which serves as a reference. See for example German patent specifications Nos. 1,955,866; 2,201,403; 2,531,759; 2,458,514 and 2,416,947. The known methods and apparatuses work as a rule with the aid of a three-dimensionally fixed laser beam serving as a guide. In the known methods after each re-positioning of the cutting machine and before renewed commencement of the driving work a survey must be carried out in which a target arranged on the machine, say on an arm carrying a cutter head, is brought into coincidence with the laser beam in order to ascertain the actual position of the machine or its deviation from the ideal position. Since the cutter head can move freely in all three dimensional directions, the known methods at best merely define a profile within which the cutter head can move freely, or else they establish the position of the cutting machine in only one direction. The cutting machine can in this latter case carry out small movements by extrapolation and the freedom of movement and working accuracy of the machine are limited. For permitting greater movement of the cutting machine it is necessary to readjust the guide laser and the cutting machine, and furthermore a three-dimensional positional determination of the cutter head is not possible since the laser is fixed and is usually in contact with the machine for only a short time. Furthermore the known methods are mostly specifically adapted to the machine, since geometrical variables of the different types of cutting machines affect the calculation of the positional co-ordinates. If the cutting machine changes its position during the cutting work, which is not impossible even if the machine is stayed, accurately profiled cutting is no longer possible.
It is a general object of the invention to provide an improved method and system with which independently of the type of machine a precise determination of the spatial position of the cutter head can be carried out at any time during the operation of the machine.